U.S. patent number 6,773,751 [Application Number 10/393,010] was granted by the patent office on 2004-08-10 for boron nitride/yttria composite components of semiconductor processing equipment and method of manufacturing thereof.
This patent grant is currently assigned to Lam Research Corporation. Invention is credited to Christopher C. Chang, John E. Daugherty, Robert J. O'Donnell.
United States Patent |
6,773,751 |
O'Donnell , et al. |
August 10, 2004 |
Boron nitride/yttria composite components of semiconductor
processing equipment and method of manufacturing thereof
Abstract
A corrosion resistant component of semiconductor processing
equipment such as a plasma chamber includes a boron nitride/yttria
composite containing surface and process for manufacture
thereof.
Inventors: |
O'Donnell; Robert J. (Alameda,
CA), Daugherty; John E. (Alameda, CA), Chang; Christopher
C. (Sunnyvale, CA) |
Assignee: |
Lam Research Corporation
(Fremont, CA)
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Family
ID: |
25015789 |
Appl.
No.: |
10/393,010 |
Filed: |
March 21, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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749924 |
Dec 29, 2000 |
6613442 |
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Current U.S.
Class: |
427/255.38;
204/192.1; 427/255.34; 427/576; 427/455; 427/255.7 |
Current CPC
Class: |
H01J
37/32477 (20130101); C23C 16/4404 (20130101) |
Current International
Class: |
C23C
16/44 (20060101); H01J 37/32 (20060101); C23C
016/34 () |
Field of
Search: |
;427/255.38,255.394,255.7,576,455 ;204/192.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2662701 |
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Dec 1991 |
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FR |
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62-103379 |
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May 1987 |
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JP |
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01275779 |
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Nov 1989 |
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JP |
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WO99/20812 |
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Apr 1999 |
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WO |
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Other References
Notification of Transmittal of the International Search Report or
the Declaration for PCT/US01/43836, dated Jun. 11, 2002. .
Written Opinion for PCT/US01,43836 Dated Aug. 1, 2002..
|
Primary Examiner: Chen; Bret
Attorney, Agent or Firm: Burns, Doane, Swecker & Mathis,
LLP
Parent Case Text
This application is a divisional application of Ser. No.
09/749,924, filed on Dec. 29, 2000, now U.S. Pat. No. 6,613,442.
Claims
What is claimed is:
1. A process of coating a surface of a component of semiconductor
processing equipment, the processing comprising: (a) optionally
depositing a first intermediate coating on a surface of a component
of semiconductor processing equipment; (b) optionally depositing a
second intermediate coating on said fist intermediate layer or on
said surface; and (c) depositing a boron nitride/yttria composite
containing coating on said component to form an outer erosion
resistant surface.
2. The coating process according to claim 1, wherein said surface
of said component comprises a metal, ceramic or polymer
surface.
3. The coating process according to claim 2, wherein said surface
is anodized aluminum.
4. The coating process according to claim 1, wherein said first
intermediate coating is not optional.
5. The coating process according to claim 4, wherein said first
intermediate coating comprises a metal, ceramic or polymer
coating.
6. The coating process according to claim 1, wherein said component
comprises a chamber wall of a plasma etching chamber.
7. The coating process according to claim 1, further comprising
forming a roughened surface on said component, said diamond contain
coating being deposited on said roughened surface.
8. The coating process according to claim 1, wherein said boron
nitride/yttria composite containing coating includes a cubic phase,
a hexagonal phase or mixtures thereof.
9. The coating process according to claim 1, wherein said boron
nitride/yttria composite containing coating comprises at least one
material other than boron nitride or yttria.
10. The coating process according to claim 9, wherein said other
material is a metal, ceramic or polymer.
11. The coating process according to claim 10, wherein said other
material is zirconia.
12. The coating process according to claim 10, wherein said other
material comprises titanium carbide, titanium boride, titanium
nitride, silicon carbide, silicon boride, silicon nitride or
mixtures thereof.
13. The coating process according to claim 9, wherein said yttria
comprises from about 60 to about 80 percent by weight of said
composite.
14. The coating process according to claim 13, wherein said boron
nitride comprises from about 20 to about 40 percent by weight of
said composite.
15. The coating process according to claim 1, wherein said boron
nitride/yttria composite containing coating is deposited by
chemical vapor deposition, plasma spray coating, sublimation, laser
vaporization, sputtering, sputtering deposition, ion beam coating,
spray coating, dip coating, evaporation coating, roll-on coating or
brush coating.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to semiconductor processing equipment
and a method of improving corrosion resistance of such
components.
2. Description of the Related Art
In the field of semiconductor processing, vacuum processing
chambers are generally used for etching and chemical vapor
deposition (CVD) of materials on substrates by supplying an etching
or deposition gas to the vacuum chamber and application of an RF
field to the gas to energize the gas into a plasma state. Examples
of parallel plate, transformer coupled plasma (TCP.TM.) which is
also called inductively coupled plasma (ICP), and
electron-cyclotron resonance (ECR) reactors and components thereof
are disclosed in commonly owned U.S. Pat. Nos. 4,340,462;
4,948,458; 5,200,232 and 5,820,723. Because of the corrosive nature
of the plasma environment in such reactors and the requirement for
minimizing particle and/or heavy metal contamination, it is highly
desirable for the components of such equipment to exhibit high
corrosion resistance.
During processing of semiconductor substrates, the substrates are
typically held in place within the vacuum chamber by substrate
holders such as mechanical clamps and electrostatic clamps (ESC).
Examples of such clamping systems and components thereof can be
found in commonly owned U.S. Pat. Nos. 5,262,029 and 5,838,529.
Process gas can be supplied to the chamber in various ways such as
by gas nozzles, gas rings, gas distribution plates, etc. An example
of a temperature controlled gas distribution plate for an
inductively coupled plasma reactor and components thereof can be
found in commonly owned U.S. Pat. No. 5,863,376. In addition to the
plasma chamber equipment, other equipment used in processing
semiconductor substrates include transport mechanisms, gas supply
systems, liners, lift mechanisms, load locks, door mechanisms,
robotic arms, fasteners, and the like. The components of such
equipment are subject to a variety of corrosive conditions
associated with semiconductor processing. Further, in view of the
high purity requirements for processing semiconductor substrates
such as silicon wafers and dielectric materials such as the glass
substrates used for flat panel displays, components having improved
corrosion resistance are highly desirable in such environments.
Aluminum and aluminum alloys are commonly used for walls,
electrodes, substrate supports, fasteners and other components of
plasma reactors. In order to prevent corrosion of the such metal
components, various techniques have been proposed for coating the
aluminum surface with various coatings. For instance, U.S. Pat. No.
5,641,375 discloses that aluminum chamber walls have been anodized
to reduce plasma erosion and wear of the walls. The '375 patent
states that eventually the anodized layer is sputtered or etched
off and the chamber must be replaced. U.S. Pat. No. 5,895,586
states that a technique for forming an erosion resistant film of
Al.sub.2 O.sub.3, AlC, TiN, TiC, AlN or the like on aluminum
material can be found in Japanese Application Laid-Open No.
62-103379.
U.S. Pat. No. 5,680,013 states that a technique for flame spraying
Al.sub.2 O.sub.3 on metal surfaces of an etching chamber is
disclosed in U.S. Pat. No. 4,491,496. The '013 patent states that
the differences in thermal expansion coefficients between aluminum
and ceramic coatings such as aluminum oxide leads to cracking of
the coatings due to thermal cycling and eventual failure of the
coatings in corrosive environments. In order to protect the chamber
walls, U.S. Pat. Nos. 5,366,585; 5,798,016; and 5,885,356 propose
liner arrangements.
For instance, the '016 patent discloses a liner of ceramics,
aluminum, steel and/or quartz with aluminum being preferred for its
ease of machinability and having a coating of aluminum oxide,
Sc.sub.2 O.sub.3 or Y.sub.2 O.sub.3, with Al.sub.2 O.sub.3 being
preferred for coating aluminum to provide protection of the
aluminum from plasma. The '585 patent discloses a free standing
ceramic liner having a thickness of at least 0.005 inches and
machined from solid alumina. The '585 patent also mentions use of
ceramic layers which are deposited without consuming the underlying
aluminum can be provided by flame sprayed or plasma sprayed
aluminum oxide. The '356 patent discloses a ceramic liner of
alumina and a ceramic shield of aluminum nitride for the wafer
pedestal. U.S. Pat. No. 5,885,356 discloses ceramic liner materials
for use in CVD chambers.
Various coatings have been proposed for metal components of
semiconductor processing equipment. For instance, U.S. Pat. No.
5,879,523 discloses a sputtering chamber wherein a thermally
sprayed coating of Al.sub.2 O.sub.3 is applied to a metal such as
stainless steel or aluminum with an optional NiAl.sub.x bond
coating therebetween. U.S. Pat. Nos. 5,522,932 and 5,891,253
disclose a rhodium coating for metal components of an apparatus
used for plasma processing of substrates with an optional nickel
coating therebetween. U.S. Pat. No. 5,680,013 discloses non-bonded
ceramic protection for metal surfaces in a plasma processing
chamber, the preferred ceramic material being sintered AlN with
less preferred materials including aluminum oxide, magnesium
fluoride, and magnesium oxide. U.S. Pat. No. 5,904,778 discloses a
SiC CVD coating on free standing SiC for use as a chamber wall,
chamber roof, or collar around the wafer.
With regard to plasma reactor components such as showerhead gas
distribution systems, various proposals have been made with respect
to the materials of the showerheads. For instance, commonly owned
U.S. Pat. No. 5,569,356 discloses a showerhead of silicon,
graphite, or silicon carbide. U.S. Pat. No. 5,494,713 discloses
forming an alumite film on an aluminum electrode and a silicon
coating film such as silicon oxide or silicon nitride over the
alumite film. The '713 patent states that the thickness of the
silicon coating film should be 10 .mu.m or less, preferably about 5
.mu.m, since the aluminum coating film, the alumite coating film
and the silicon coating film have different coefficients of linear
expansion and cracks are easily generated when the thickness of the
silicon coating film is too thick. A thickness below 5 .mu.m,
however, is stated to be unfavorable since the protection of the
aluminum substrate is insufficient. U.S. Pat. No. 4,534,816
discloses an upper showerhead electrode of stainless steel,
aluminum, copper or the like. U.S. Pat. No. 4,612,077 discloses a
showerhead electrode of magnesium. U.S. Pat. No. 5,888,907
discloses a showerhead electrode of amorphous carbon, SiC or Al.
U.S. Pat. Nos. 5,006,220 and 5,022,979 disclose a showerhead
electrode either made entirely of SiC or a base of carbon coated
with SiC deposited by CVD to provide a surface layer of highly pure
SiC.
In view of the need for high purity and corrosion resistance for
components of semiconductor processing equipment, there is a need
in the art for improvements in materials and/or coatings used for
such components. Moreover, with regard to the chamber materials,
any materials which can increase the service life of a plasma
reactor chamber and thus reduce the down time of the apparatus,
would be beneficial in reducing the cost of processing the
semiconductor wafers.
SUMMARY OF THE INVENTION
According to a first aspect of the invention a process for
providing an erosion resistant boron nitride/yttria composite
containing coating on a surface of a semiconductor processing
equipment component is provided. The process includes depositing a
boron nitride/yttria composite containing coating on a surface of a
processing equipment component so as to form an outer erosion
resistant surface. By erosion resistant surface, it is meant a
surface coating that protects underlying materials from the
corrosive effects of plasma chamber gases, while resisting erosion
of the coating by the plasma chamber gases. The underlying surface
of the process equipment component to be coated can comprise a
metal, ceramic or polymer material with a preferable material being
anodized aluminum.
In a preferred embodiment, one or more intermediate metal, ceramic
or polymer coatings may be used between the surface of the
semiconductor processing equipment and the boron nitride/yttria
composite containing coating. Metal surfaces that may be coated
include anodized or unanodized aluminum, stainless steel, a
refractory metal such as molybdenum or other metal or alloy used in
plasma chambers. Ceramic surfaces that may be coated include
alumina, SiC, AlN, Si.sub.3 N.sub.4, BC or other plasma compatible
ceramic material. Polymeric surfaces that may be coated include
fluoropolymers such as Teflon.RTM., polyimides such as Vespel.RTM.,
and other polymeric materials useful in a plasma chamber at
temperatures up to 200.degree. C.
According to a second aspect of the invention, a metal component is
provided. The component includes: (a) a metal surface; (b) an
optional first intermediate coating on the metal surface; (c) an
optional second intermediate coating on the first intermediate
coating or on the metal surface; and a boron nitride/yttria
composite containing coating on said component which provides a
corrosion resistant outer surface. Each of the first and second
intermediate coatings may be a metal or alloy thereof, ceramic,
polymer or mixture or composite of materials used in plasma chamber
reactors.
According to another aspect of the invention, there is provided a
semiconductor processing equipment component made of a boron
nitride/yttria composite containing material. The component may
include any one or more coatings employed in such equipment.
BRIEF DESCRIPTION OF THE DRAWINGS
The objects and advantages of the invention will become apparent
from the following detailed description of the preferred
embodiments thereof in connection with the accompanying drawing, in
which:
FIG. 1 is a schematic cross-sectional view of a plasma reactor
chamber having a component coated with a corrosion resistant
coating in accordance with the present invention.
FIG. 2 shows details of the corrosion resistant coating in detail A
of FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE
INVENTION
The invention provides an effective way to provide corrosion
resistance to metal, ceramic and polymer surfaces of components of
semiconductor processing apparatus such as parts of a plasma
processing reactor chamber by utilizing an erosion resistant
coating. Such components include chamber walls, substrate supports,
gas distribution systems including showerheads, baffles, rings,
nozzles, etc., fasteners, heating elements, plasma screens, liners,
transport module components, such as robotic arms, fasteners, inner
and outer chamber walls, etc., and the like.
Although the invention is applicable to any type of component
having a metal, ceramic or polymer surface, for ease of
illustration, the invention will be described in more detail with
reference to the apparatus described in U.S. Pat. No. 5,820,723
which is incorporated herein by reference in its entirety.
FIG. 1 illustrates a vacuum processing reactor chamber 10 that
includes a substrate holder 70 providing an electrostatic clamping
force to a substrate 60 as well as providing an RF bias to the
substrate while it is He backcooled. A focus ring 72 confines
plasma in an area above the substrate. A source of energy for
maintaining a high density (e.g., 10.sup.11 -10.sup.12
ions/cm.sup.3) plasma in the chamber such as an antenna 40 powered
by a suitable RF source to provide a high density plasma is
disposed at the top of reactor chamber 10. The chamber includes
suitable vacuum pumping apparatus for maintaining the interior 30
of the chamber at a desired pressure (e.g., below 50 mTorr,
typically 1-20 mTorr) by evacuating the chamber through the
centrally located vacuum port 20 at the bottom of the chamber.
A substantially planar dielectric window 50 of uniform thickness
provided between the antenna 40 and the interior of the processing
chamber 10 forms the vacuum wall at the top of the processing
chamber 10. A gas distribution plate 52 is provided beneath window
20 and includes openings such as circular holes for delivering
process gas from a gas supply to the chamber 10. A conical liner 54
extends from the gas distribution plate and surrounds the substrate
holder 70.
In operation, a semiconductor substrate such as a silicon wafer 60
is positioned on the substrate holder 70 and is typically held in
place by an electrostatic clamp 74 while He backcooling is
employed. Process gas is then supplied to the vacuum processing
chamber 10 by passing the process gas through a gap between the
window 50 and the gas distribution plate 52. Suitable gas
distribution plate arrangements (i.e., showerhead) are disclosed in
commonly owned U.S. Pat. Nos. 5,824,605; 6,048,798; and 5,863,376,
the disclosures of which are hereby incorporated by reference. For
instance, while the window and gas distribution plate arrangement
in FIG. 1 are planar and of uniform thickness, non-planar and/or
non-uniform thickness geometries can be used for the window and/or
gas distribution plate. A high density plasma is ignited in the
space between the substrate and the window by supplying suitable RF
power to the antenna 40.
Chamber walls 28 such as anodized or unanodized aluminum walls and
metal, ceramic or polymer components such as the substrate holder
70, fasteners 56, liners 54, etc., that are exposed to plasma and
show signs of corrosion are candidates for coating according to the
invention, thus avoiding the need to mask them during operation of
the plasma chamber. Examples of metals and/or alloys that may be
coated include anodized or unanodized aluminum and alloys thereof,
stainless steel, refractory metals such as W and Mo and alloys
thereof, copper and alloys thereof, etc. Examples of ceramic
surfaces that may be coated include alumina, SiC, AlN, Si.sub.3
N.sub.4, BC and TiO.sub.2. Examples of commercially available
polymer materials that may be coated include fluoropolymers such as
Teflon.RTM., polyimides such as Vespel.RTM., and other polymeric
materials useful in a plasma chamber at temperatures up to
200.degree. C. In a preferred embodiment, the component to be
coated is a chamber wall 28 having an anodized or unanodized
aluminum surface 29. The coating according to the invention permits
use of aluminum alloys without regard as to its composition (thus
allowing use of more economical aluminum alloys in addition to
highly pure aluminum), grain structure or surface conditions. In
the following discussion, an example of a component to be coated is
an aluminum chamber wall 28 having a first optional intermediate
coating 80, a second optional intermediate coating 90 and a boron
nitride/yttria composite containing coating 100, as illustrated in
FIG. 2.
In order to ensure good adhesion of the coated material, the
surface of the aluminum substrate 28 is preferably thoroughly
cleaned to remove surface material such as oxides or grease prior
to coating. In addition, it is particularly desirable to roughen
the substrate surface, anodize the substrate surface and again
roughen the anodized substrate surface prior to application of any
of the desired coatings.
According to the invention, a first intermediate coating 80 is
optionally coated on the aluminum sidewall 28 by a conventional
technique. The optional first intermediate coating 80 is
sufficiently thick to adhere to the substrate and to further allow
it to be processed prior to forming the optional second
intermediate coating 90 or the diamond containing coating described
below. The first intermediate coating 80 can have any suitable
thickness such as a thickness of at least about 0.001 inches,
preferably from about 0.001 to about 0.25 inches, more preferably
between 0.001 and 0.1 inches and most preferably from 0.001 inches
to 0.05 inches.
After depositing the optional first intermediate coating 80 onto
aluminum substrate 28, the plating can be blasted or roughened by
any suitable technique, and then overcoated with the second
optional coating 90 or the boron nitride/yttria composite
containing coating 100. A roughened layer 80 provides a
particularly good bond. Desirably, the second intermediate coating
90 imparts a high mechanical compression strength to the coating 80
and minimizes formation of fissures in the coating 90.
The optional second intermediate coating 90 is sufficiently thick
to adhere to the first intermediate coating 80 and to further allow
it to be processed prior to forming any additional intermediate
coatings or the outer boron nitride/yttria composite containing
coating 100 described below. The second intermediate coating 90 can
have any suitable thickness such as a thickness of at least about
0.001 inches, preferably from about 0.001 to about 0.25 inches,
more preferably between 0.001 and 0.1 inches and most preferably
between 0.001 inches and 0.05 inches.
The first and second intermediate coating may be made of any one or
more materials employed in conventional plasma processing chambers.
Examples of such materials include metals, ceramics and polymers.
Particularly desirable metals include any one or more refractory
metals, composites or alloys containing such metals. Particularly
desirable ceramics include Al.sub.2 O.sub.3, SiC, Si.sub.3 N.sub.4,
BC, AlN, TiO.sub.2, etc. Particularly desirable polymers include
fluoropolymers such as Teflon.RTM., polyimides such as Vespel.RTM.,
and other polymeric materials useful in a plasma chamber at
temperatures up to 200.degree. C. Specific materials contemplated
for the intermediate layers also include fullerene containing
materials; other hard carbon containing materials such as diamond
and diamond-like materials; carbides, borides, nitrides and/or
carbonitrides of, for example, hafnium, tantalum, titanium and/or
silicon; boron carbides; boron nitrides; boron carbonitrides;
zirconia; yttria or mixtures of any of the above-mentioned
materials.
It is contemplated that the first and second intermediate layers 80
and 90, which are optional may be any one of the above-mentioned
materials such that the coatings are the same or different
depending on the desired properties. It is also anticipated that
additional intermediate coatings such as a third, fourth or fifth
intermediate coating of the same or different materials may be
employed.
The boron nitride/yttria composite containing coating 100 is
deposited on the optional second intermediate coating 90, or on the
optional first intermediate coating 80, or on the aluminum
substrate 28. The thickness of the boron nitride/yttria composite
containing coating is desirably at least 0.001 inches; preferably
from about 0.001 to about 0.25 inches, more preferably from about
0.001 to about 0.1 inches and most preferably from 0.001 to 0.05
inches. The thickness of the boron nitride/yttria composite
containing coating 100 can be selected to be compatible with the
plasma environment to be encountered in the reactor (e.g., etching,
CVD, etc.). This layer of boron nitride/yttria composite containing
coating may be coated on all or part of the reactor chamber and
components as discussed above. Most desirably, the boron
nitride/yttria composite coatings are of a thickness useful to
provide erosion and/or corrosion protection to the underlying
layers, and particularly the substrate, for a significant period of
exposure to the corrosive chamber gases.
The boron nitride/yttria composite containing coating 100 of the
present invention contains both boron nitride and yttria. The boron
nitride component of the composite may be any one of hexagonal,
cubic or mixtures thereof. Most desirably the boron nitride
component is 100% cubic phase or contains proportions of cubic
phase exceeding 60% by weight, preferably exceeding 80% by weight
and most preferably exceeding 90% by weight. The cubic form of
boron nitride has a much higher density, is very hard and may be
produced from the hexagonal form at high temperature and pressure.
Alternatively, the boron nitride may be 100% hexagonal phase.
The yttria component of the composite may be present in an amount
between about one percent and 99 percent, more desirably between
about 40 and 99 percent and even more desirably between about 60
and 80 percent of the total composite. The boron nitride component
may be present in an amount between about one percent and 99
percent, more desirably between about one and 60 percent and even
more desirably between about 20 and 40 percent of the total
composite.
The composite may include other protective materials in amounts up
to about fifty percent of the total composite or greater.
Desirably, boron nitride, yttria or zirconia form a continuous
matrix phase in such composites. More desirably, the composites of
the present invention include between about one and 40 percent by
weight additional material, and more preferably between about one
and 20 percent by weight additional material and even more
preferably between about one and 10 percent by weight additional
material based upon the composite.
Such materials may include any one or more materials employed in
plasma processing chambers. Examples of such materials include any
one or more metals, ceramics or polymers. Particularly desirable
metals include any one or more refractory metals, composites or
alloys containing such metals. Particularly desirable ceramics
include Al.sub.2 O.sub.3, SiC, Si.sub.3 N.sub.4, BC, AlN,
TiO.sub.2, etc. Particularly desirable polymers include
fluoropolymers such as Teflon.RTM., polyimides such as Vespel.RTM.
and other polymeric materials useful in a plasma chamber at
temperatures up to 200.degree. C. It is believed that the most
desirable materials would include a boron nitride/yttria composite
alone or in combination with carbides, borides, nitrides and/or
carbonitrides of, for example, hafnium, tantalum, titanium and/or
silicon; boron carbides; boron nitrides; boron carbonitrides;
zirconia; yttria or mixtures of the above-mentioned materials.
The boron nitride/yttria composite containing coating 100 of the
present invention may be deposited onto the desired surface by any
known coating technique such as thermal spraying, plasma spraying,
chemical vapor deposition, sublimation, laser vaporization,
sputtering, sputter deposition, ion beam coating, spray coating,
dip coating, evaporation, roll-on coating brush coating, etc. It is
also contemplated that multiple boron nitride/yttria composite
containing coatings with or without intermediate layers of other
materials may be deposited onto the desired surface using any
suitable technique.
In an alternative aspect of the invention, there is provided a
semiconductor processing equipment component made of a boron
nitride/yttria composite containing material. The component may
include any one or more coatings conventionally employed in such
equipment.
By use of the boron nitride/yttria composite containing coatings or
components of the present invention, it is preferred to obtain an
ultrahard, erosion resistant surface. Such coating or component is
desirably free of materials that react with processing chamber
gases and is chemically inert such that there is low or no particle
contamination, little or no corrosion, little or no metal
contamination and/or little or no volatile etch products.
It is preferred that boron nitride/yttria composite containing
coating or component be placed in the regions that may or may not
be exposed to the plasma environment such as parts in direct
contact with the plasma or parts behind chamber components such as
liners, etc., to prevent metal contamination of the semiconductor
substrates processed in the reactor chamber. It is particularly
preferred to limit or exclude transition metal dust; e.g., any one
or more of elements 21 through 29 (scandium through copper), 39
through 47 (yttbrium through silver), 57 through 79 (lanthanum
through gold) and all known elements from 89 (actinium) on in the
Periodic Table. Thereby, according to one advantage of the present
invention, unsatisfactory etching or undesirable formation of
pinholes in deposited films is reduced by suppressing occurrence of
such dust by either erosion or corrosion.
While the invention has been described in detail with reference to
specific embodiments thereof, it will be apparent to those skilled
in the art that various change and modifications can be made, and
equivalents employed, without departing from the scope of the
appended claims.
* * * * *